Identification

Description

Valves are asymmetric to the apical axis; the dorsal margin is highly arched and convex, while the ventral margin is concave. A central, unilateral swelling is present on the ventral margin. Ghost striae may be present in the central swelling. Valve apices are capitate to attenuate. A narrow, distinct central sternum is present. One to two rimoportulae are present at the valve apices.

Autecology

Hannaea arcus is found in cool flowing water in mountainous regions across the US.

Cite This Page

Kociolek, P. (2010).
Hannaea arcus.
In Diatoms of North America.
Retrieved June 07, 2020, from https://diatoms.org/species/hannaea_arcus

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Hannaea arcus from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)STRAHLER = distribution plot of the Strahler Stream Order SLOPE = stream reach gradient (degrees)W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.PHSTVL = pH measured in a sealed syringe sample (pH units)log_COND = log concentration of specific conductivity (µS/cm)log_PTL = log concentration of total phosphorus (µg/L)log_NO3 = log concentration of nitrate (µeq/L)log_DOC = log concentration of dissolved organic carbon (mg/L)log_SIO2 = log concentration of silicon (mg/L)log_NA = log concentration of sodium (µeq/L)log_HCO3 = log concentration of the bicarbonate ion (µeq/L)EMBED = percent of the stream substrate that is embedded by sand and fine sedimentlog_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.

Hannaea arcus

(Ehrenb.) R.M.Patrick 1966

Apices capitate to attenuate

Dorsal margin convex

Central swelling on ventral margin

Rimoportulae 1-2

Apices are capitate to attenuate. The dorsal margin is highly arched and convex, while the ventral margin is concave with a swelling of the central area. The central sternum is distinct and narrow. A rimoportula is present near the valve ends and is often visible in the light microscope. Striae are parallel.